Recently, with rapid dissemination of information and the fast development of electronic technology, the Internet has become an information collection and distribution center accessible anywhere in the world. According to statistics, the amount of information generated by global media networks in 2003 totals five billion gigabytes (GB, or 109 bytes), which is equivalent to the amount of information generated by man in the past five thousand years. From 2003 onward, network technology has advanced even faster. Nowadays, it is estimated that network users around the world generate at least 100 billion entries of Internet search records each month—a compelling evidence of people's dependence on networks. Seeing that networks are almost indispensible in modern life, be it for playing online games, marketing, travel planning, making medical appointments, or even inquiring about bus arrival time, the related industry has endeavored to increase the convenience and stability of networks in various environments.
Generally speaking, one who wishes to connect to the Internet and use related services must connect an Ethernet cable to a computer device so that Internet connection can be correctly made through the routing function of the computer device. Thus, the extent over which Ethernet cables are distributed in a place determines, in a way, the area where network connection is possible. With the advent of mobile electronic devices (e.g., laptop computers, smart phones, personal digital assistants, and so on), however, mechanisms for wireless network communication have gradually matured and been widely used, making it possible to make Internet connection without limitation by the distribution of physical lines. Nevertheless, wireless signals attenuate significantly when passing through a concrete wall or a human body. If wireless signals are used where there are plenty of such barriers, signal transmission may be interrupted frequently; in other words, the stability of signal transmission is not guaranteed.
In view of the difficulty of Ethernet cable distribution and the adverse effects of the aforesaid barriers on wireless network signals, power line communication (PLC) technology was developed. As its name suggests, power line communication relies on existing power lines in a building to transmit network signals. In order to apply PLC technology, PLC devices (e.g., network bridges) are required, which are connected to power line sockets at different locations to convert network signals and thereby enable transmission of network signals via power lines. Now that power lines are essential to each building, using power lines as the backbone medium for network transmission not only spares the trouble of cable distribution, but also reduces the cost and time of construction. Also, the integrity of the interior design of a building need not be compromised. In a nutshell, PLC is an ideal solution to the aforesaid problems. In practice, however, the PLC technology has its own problems, two major ones of which are detailed as follows:
(1) Taking up extra socket space: A typical power line socket outlet has two or more sockets, but the spacing between each two adjacent sockets is quite limited and far smaller than the size of a PLC device. Therefore, when a PLC device is connected to such a socket outlet, chances are it takes up the space of more than one socket, preventing the socket outlet from supplying power to other appliances in that area. Although a power strip can be used to solve this problem, the surge protection elements in a power strip tend to lower the signal intensity of the PLC device significantly, for the surge protection elements, which are provided to ensure safety, will identify network signals as surges.
(2) Noise interference: As a power line is designed solely as a power-supplying medium in the first place and is not configured for high-quality signal transmission, the voltage carried by a power line will fluctuate with the load of the electronic device being powered or even generate electromagnetic radiation. The electronic device being powered may also generate noise. All the foregoing interferes with network signals. A minor interference can lower the quality of network signal transmission; a significant interference, on the other hand, can destroy network signals completely.
One solution to the aforesaid problem is to install a filter in the PLC device, so as for the filter to filter out noise in the power line. However, since not all electronic devices generate a high level of noise, one who has bought a PLC device equipped with a filter can never know if the filter provides the expected filtering effect, or which electronic device should the PLC device be connected to in order to filter out the strongest source of noise. Hence, the issue to be addressed by the present invention is to design a PLC device which not only can effectively detect noise generated by various electronic devices, but also can filter out the noise detected, thereby increasing the quality of a network environment.